Correct Answer: A

Rationale: The correct answer is 'tissues, which build organs.' Specialized cell types organize to form tissues, which in turn build organs. Tissues are groups of cells that work together to perform a specific function. Option B is incorrect because organs are composed of tissues, not the other way around. Option C is incorrect as organ systems consist of multiple organs working together, not building tissues. Option D is incorrect as atoms are the basic building blocks of matter and are not directly involved in forming tissues.

Correct Answer: D.

Rationale: The correct answer is 'excretion.' Excretion is the process of eliminating waste products produced by metabolic reactions from the body. Metabolism (Choice A) refers to the chemical processes that occur within a living organism to maintain life. Absorption (Choice B) is the process of taking in nutrients and fluids into the body. Assimilation (Choice C) is the process of absorbing and incorporating nutrients into the body after digestion. Therefore, excretion is the most appropriate term for the removal of metabolic wastes.

Correct Answer: C

Rationale: Wrinkled and sagging skin is primarily caused by the loss of subcutaneous fat and reduced levels of elastin and collagen in the skin. Choice A is incorrect as drinking too much water does not lead to wrinkled and sagging skin. Choice B is incorrect because heredity alone does not cause this condition. Excess subcutaneous fat, as mentioned in Choice D, can contribute to a different skin appearance, such as puffiness, but not wrinkled and sagging skin.

Correct Answer: A

Rationale: The correct answer is 'tissues, which build organs.' Specialized cell types organize to form tissues, which in turn build organs. Tissues are groups of cells that work together to perform a specific function. Option B is incorrect because organs are composed of tissues, not the other way around. Option C is incorrect as organ systems consist of multiple organs working together, not building tissues. Option D is incorrect as atoms are the basic building blocks of matter and are not directly involved in forming tissues.

Correct Answer: A

Rationale: The correct answer is A: Monomers. Macromolecules are built from smaller subunits called monomers. Monomers join together through chemical reactions to form larger molecules known as macromolecules. Option B is incorrect because it does not provide the accurate information regarding macromolecules. Option C is incorrect as it indicates uncertainty, which is not the case here. Option D is incorrect as there is a specific answer related to the composition of macromolecules.